The data in the table below was derived by timing how long it took the EOS Digital Rebel/300D to write out 4 Large Fine JPEG and 4 RAW .CRW photos to the card. Timing commenced when the camera's card status light illuminated, and stopped when the light went out. Each test cycle was performed 3 times (if the card's capacity allowed for that) to ensure accurate results.

Card-to-card speed variation within the same brand and model, photographing scenes of varying detail and at different ISO settings - these and other factors may slightly alter write speed performance. As a result, write speed differences of 5% or less from card to card in the table below should be considered insignificant. If one card's write speed is within 5% of another's, the two cards are likely to offer effectively the same performance in the real world. Similarly, it's unlikely that most photographers would notice a difference between the fastest card and one that was up to 10% slower.

The results are arranged in the table from fastest to slowest (based on JPEG write speed). The top 10% (based on JPEG write speed) are marked in blue.

(1) To help determine whether the card you purchase is substantially similar to the one tested, the card's description includes an identifier - series number, internal name or other unique value - where possible and applicable.(2) Many companies sell CompactFlash media; relatively few actually design and manufacture the key internal components, including the controller and flash memory. This column lists the manufacturer of the controller.(3) Type I CompactFlash cards are 3.3mm in thickness; Type II, 5.0mm.(4) K/sec = Kilobytes per second (1 kilobyte = 1024 bytes); MB/sec = Megabytes per second (1 megabyte = 1024 kilobytes).(5) Companies that source CompactFlash cards from Toshiba may opt for either the faster binary-type (often called single level cell, or SLC) or slower (but less expensive to manufacture) multi level cell (MLC) architecture. Kingston's standard orange-labeled line uses Toshiba MLC; the Elite Pro line uses either Toshiba SLC or Samsung.(6) Delkin has not revealed the design and manufacturing partner for their PRO line of CompactFlash cards up to 640MB; above that capacity, the cards we tested were sourced from Samsung.(7) These cards contain controllers from an unknown manufacturer, likely of Taiwanese origin.(8) This camera's built-in formatter will reformat cards over 2GB as FAT32 with a 4K cluster size. This cluster size usually means less efficient camera-to-card transfers than FAT32 formatting with a 32K cluster size, so we've tested FAT32-formatted cards both ways in this camera. The only way with this camera to format a card FAT32 with a 32K cluster size is on the computer: we used the Format function in Disk Management in Windows XP. Note that technical staff at two CF card manufacturers warned that if a camera isn't designed for FAT32 with cluster sizes larger than 4K that compatibility problems could arise (though we experienced none in our testing).(9) This card, which began to ship in mid-March 2004, contains faster memory than the original 40X card. Lexar has revamped their entire 40X Pro Series lineup, from 256MB to 4GB, with the faster memory, though we've only tested the 1GB model. The packaging for the revamped 40X doesn't indicate that the card inside is different from an original 40X, though the card itself does: if the series number stamped on the card's edge ends in C977, it's a revamped 40X.(10) Lexar began shipping their 80X line of cards in late June 2004. The card marked *first edition* in the table is a production model representative of the 80X lineup that began shipping at that time. In October 2004, Lexar began to ship a revised version of their 80X cards, which we've dubbed *second edition* here. As of this writing, the first edition and second edition cards are identical in appearance and sold in the same retail packaging. Only the last four digits of the edge stamp differentiate first edition from second edition. If the last four digits are A4B6, it's almost certainly a second edition 80X CompactFlash card. Please see this article for more information on the status of Lexar 80X second edition cards.(11) This card includes a switch that enables it to operate as either a 2GB or 4GB card, for compatibility with older cameras that are unable to recognize cards over 2GB. All testing in this camera has been done with the card's switch set to the 4GB position. See the next note for more information on this card.(12) In October 2004, Sandisk announced that its Ultra II line of memory cards was being revamped to utilize multi level cell flash memory instead of the binary-type flash memory (often referred to as SLC) used in Ultra II since the fall of 2003. As of this writing, we're not sure how a prospective purchaser will be able to differentiate older, binary-type Ultra II CompactFlash cards from newer, MLC Ultra II CompactFlash cards, or how soon MLC Ultra II was going to be widely available from retailers. As of this writing, all Ultra II CF, including the 4GB capacity, utilizes binary-type memory. We have no plans to test the 4GB Ultra II binary-type, because it was expected to be shipping for no more than about a month before being replaced by the MLC version tested here.